Charging air conditioning system

rbrunckhorst · 06-05-05, 08:13 PM

Does anybody know how much 134a refrigerant to put in the system. How about the amount of oil? Any speical procedures? Do we need to vacuum test the system prior to charging it? [img]/ubbthreads/images/graemlins/tongue.gif[/img]

**patbarry** · 06-05-05, 09:22 PM

I plan on having a professional do this for just these types of reasons. Plus I see no reason to go through multiple dryers.

I do believ the answer to your question is, yes, the system must first be evacuated prior to charging. I seem to remember a rough rule of thumb was that one can of oil went in with two or three cans of refrigerant, but that's 15+ years ago with the old R12 (or was it R22?), and that was for recharges, not wholly new start-ups.

rbrunckhorst · 06-05-05, 11:49 PM

One can rent all the gauges and vacuum pumps at Autozone. They even sell a DVD detailing how to do it. It's realy just a matter of knowing how much of what to put in the system. Unfortunately its not in the manual.

Phil · 06-06-05, 12:32 AM

rBrunckhorst
Charging the system is nat at all a difficult proceedure, but in your case the system is probably not marked as to how much refrigerant to use (most production vehicles are clearly marked. This is really only a guideline anyway. I would suggest that you make sure that your receiver/dryer is new, make sure the expansion orifice is clear, or just put a new one in, and vacuum the system for about 1/2 hour to boil off any moisture that is in there.
You can figure out the charge a couple of ways. One is a sight glass which you may not have.Or look at a chart for a current production vehicle and measure under hood ambient temperature and charge until your high side reads to the corresponding pressure (approximate), or most tool manufacturers have a clamp on tool that goes on the metal lines and sonically looks for air bubbles.
All of these methods work well, depending on the system, but I have found that common sense goes a long way and if you are charging the system and it suddenly gets warmer you may have too much refrigerant....time to bleed off a little.
The bottom line is put in the correct oil, if the system cools well after charging, you are probably in the ball park.
Just be careful with hoses and connections as there are some very high pressures to deal with.
Good Luck
Phil

Hershal Byrd · 06-06-05, 12:40 AM

Sorry Rolf for not having this in the manual. This is one of those areas where I let the professional Handle it .
On the top of the dryer there is a sight glass. It my have a sticker over it. Just remove it. One can of oil is all I remember being put into my system while watching the pro. As he was charging the system with freon he asked me to keep an eye on the sight glass. He said to let him know when there were no more bubbles passing by the glass. As soon as I saw that I told him and he stopped the process. That was almost four years ago and the system is still going strong.

Hersh [img]/ubbthreads/images/graemlins/smile.gif[/img]

Mark Clapp · 06-06-05, 12:56 AM

I first put in one can of 134a type oil, one can of stop leak, and one can of Maxi-Cool. These are small cans and are sourced the cheapest at Wal-Mart. I then filled with the 134a (regular sized can) using the low pressure side gauge that comes on the fill line they sell with the other refridgerant stuff. Two or so cans filled the system with the gauge reading around 45-47 lbs, again on the suction or low pressure side. The Maxi-Cool is a line conditioner and really helps to keep the coolant in the system. Now each summer or so I just add a can of coolant to top off the system.

Eric · 06-06-05, 01:58 AM

Mark, I dont know much about what AC system you are running so I may be wrongm, but 45 lbs on the low side with the ac running seems a bit on the high side. With everything working right, I would expect to see about half that. Also, if you need to add a can of refrigerent every year, you have a slow leak. You can buy AC dye that you put in and search for the leak with an infrared light, works very well.

rbrunckhorst · 06-06-05, 07:25 AM

Thanks guys. This should give me enough info to get started.

Ron Earp · 06-06-05, 08:16 AM

20-25lbs on the low side on any modern system, almost irregardless of make. Mark if you have that much, and you think the gauge is correct, then if you bleed some off you'll have much better cooling.

Mark Clapp · 06-06-05, 11:06 AM

Yes, I rechecked the gauge and the "filled" zone is from 25 to 45 lbs so you guys are correct. I do have a slow leak somewhere and need to sniff that out, but it is easy to add a little as needed with the new system.

Pat Buckley · 06-06-05, 01:18 PM

[ QUOTE ]
One can rent all the gauges and vacuum pumps at Autozone. They even sell a DVD detailing how to do it. It's realy just a matter of knowing how much of what to put in the system. Unfortunately its not in the manual.

[/ QUOTE ]

Apparently the Autozone stores around here (Northern CA) do not rent the equipment needed....

Darn.

Phil · 06-06-05, 11:17 PM

Rolf
Eric and Ron are correct with those pressures, I would think that your high side should read about 275 to 350 PSI depending on ambient temp. The key here is the pressure differential between the two sides, the greater the difference the better the cooling.

Ron Earp · 06-07-05, 11:28 AM

Hate to say it, but I have had great luck with no gauges (I have some now) in the past. If empty I'd simply put 2-3 cans in the system, basically til it quit taking them, and it seemed to always work out well - I had cool air, the system worked, and I experienced no problems.

I now use gauges but nothing has changed, I still get working systems. Oh, you can get EPA certified on the web to handle Freon 12 - I did, so I could charge some older non-converted systems. Got me a little card that says I'm good to go!